Relay apparatus and relay method

ABSTRACT

There is provided a relay apparatus including a memory, and a processor coupled to the memory and the processor configured to receive a first packet including an identifier for indicating a content, determine whether or not the content indicated by the identifier included in the first packet is saved in a cache, transmit a second packet including a source address of the first packet and the identifier when it is determined that the content is not saved in the cache, and transmit a third packet including an address of the relay apparatus and the identifier when it is determined that the content is saved in the cache.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of theprior Japanese Patent Application No. 2016-141695, filed on Jul. 19,2016, the entire contents of which are incorporated herein by reference.

FIELD

The embodiments discussed herein are related to a relay apparatus and arelay method.

BACKGROUND

In recent years, for example, a network technology called contentcentric networking (CCN) has been known for distributing contents suchas videos and audios. CCN is also called, for example, informationcentric networking (ICN) or named data networking (NDN). CCN allows auser to acquire desired contents by using a contents name indicating thedesired contents as a key without being conscious of the location of aserver in which the desired contents are stored.

A user terminal transfers an Interest packet including the content nameindicating the desired contents to the server via a relay node in anetwork. The relay node relays the Interest packet by Hop-by-Hopcommunication. Then, when the Interest packet is received, the serveracquires the contents corresponding to the contents name in the Interestpacket from a storage destination. The server transfers the contents toeach relay node on a path through which the Interest packet istransferred. When the contents are received, each relay node stores thereceived contents in a cache. Then, the relay node transfers thecontents stored in the cache to the user terminal.

Related technologies are disclosed in, for example, Japanese Laid-OpenPatent Publication No. 2013-179482 and Japanese Laid-Open PatentPublication No. 2015-136098.

SUMMARY

According to an aspect of the invention, a relay apparatus includes amemory, and a processor coupled to the memory and the processorconfigured to receive a first packet including an identifier forindicating a content, determine whether or not the content indicated bythe identifier included in the first packet is saved in a cache,transmit a second packet including a source address of the first packetand the identifier when it is determined that the content is not savedin the cache, and transmit a third packet including an address of therelay apparatus and the identifier when it is determined that thecontent is saved in the cache.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory view illustrating an example of a CCN systemaccording to a first embodiment;

FIG. 2 is an explanatory view illustrating an example of a relay node;

FIG. 3 is an explanatory view illustrating an example of the entryconfiguration of FIB;

FIG. 4 is an explanatory view illustrating an example of the entryconfiguration of PIT;

FIG. 5 is an explanatory view illustrating an example of the entryconfiguration of a conversion table;

FIG. 6 is an explanatory view illustrating an example of a processingoperation in a CCN system related to contents request processing;

FIG. 7 is an explanatory view illustrating an example of a processingoperation in a CCN system related to contents transfer processing;

FIG. 8 is a sequence diagram illustrating an example of a series ofprocessing operations in a CCN system from contents request to contentsacquisition;

FIG. 9 is a flowchart illustrating an example of a processing operationof a relay node related to reception processing;

FIG. 10 is a flowchart illustrating an example of a processing operationof a relay node related to relay processing;

FIG. 11 is an explanatory view illustrating an example of a processingoperation from contents request to contents acquisition in a CCN systemaccording to a second embodiment; and

FIG. 12 is an explanatory view illustrating an example of a processingoperation from contents request to contents acquisition of a CCN systemaccording to a third embodiment.

DESCRIPTION OF EMBODIMENTS

Each relay node in a CCN system may set whether or not a cache isrequired, that is, whether or not to save received contents in a cache,based on a predetermined algorithm. That is, in a relay node on a paththrough which an Interest packet is transferred, received contents aresaved in a cache when the cache is required, but the received contentsare not saved in a cache when the cache is not required. Therefore, itis unnecessary to transfer the received contents to a relay node inwhich the cache is not required among a plurality of relay nodes on thepath through which the Interest packet is transferred.

However, since the received contents are also transferred to the relaynode in which the cache is not required, the time required fortransferring the received contents becomes long, and the transfer rateof the received contents is lowered. Therefore, an optimal routing maybe performed to increase the transfer rate of the received contents.

Embodiments of a relay apparatus and a relay method capable ofincreasing a transfer rate will be described in detail below withreference to accompanying drawings. However, the disclosed technology isnot limited by these embodiments. Further, these embodiments may beappropriately combined with each other within a scope that does notcause inconsistency.

First Embodiment

FIG. 1 is an explanatory view illustrating an example of a CCN system 1according to a first embodiment. The CCN system 1 illustrated in FIG. 1includes a user terminal 2, a server 3, a plurality of relay nodes 4,and a plurality of IP routers 5. The user terminal 2 is a communicationterminal used by a user, for example, a personal computer, a smartphoneor the like. The server 3 is a server that stores contents. The relaynodes 4 are CCN-compliant relay nodes that connect between the userterminal 2 and the server 3. For convenience of explanation, the relaynodes 4 illustrated in FIG. 1 are assumed as six relay nodes 4 of #1 to#6. The IP routers 5 are IP-compliant routers that connect between theuser terminal 2 and the server 3. For convenience of explanation, the IProuters 5 illustrated in FIG. 1 are assumed as three IP routers 5 of #ato #c. Not only the relay nodes 4 but also the IP routers 5 are in astate of being mixed between the user terminal 2 and the server 3. Therelay nodes 4 relay signals by Hop-by-Hop communication.

FIG. 2 is an explanatory view illustrating an example of a relay node 4.As illustrated in FIG. 2, the relay node 4 includes a network interface(NWIF) 11, a memory 12, a control processing unit (CPU) 13, and a bus14. The NWIF 11 is, for example, an IF responsible for communicationwith the user terminal 2, the server 3, the relay nodes 4, the IProuters 5 and so on. The memory 12 is an area storing various programsand information related to the relay nodes 4. The CPU 13 controls theentire relay nodes 4. The bus 14 is a bus that mutually communicatesdata between the NWIF 11, the memory 12, and the CPU 13. The relay nodeis an example of a relay apparatus.

In addition, the functions executed by the CPU 13 in the memory 12include a CCN layer function 13A, a transport layer function 13B, and anIP layer function 13C. The CCN layer function 13A is a function executedwith the protocol of the CCN layer. The transport layer function 13B isa function executed with the protocol of the transport layer. The IPlayer function 13C is a function executed with the protocol of the IPlayer.

The CCN layer function 13A includes an Interest control unit 21, a cachecontrol unit 22, a contents transfer unit 23, and a path setting unit24. The Interest control unit 21 generates an Interest packet forrequesting the server 3 to provide contents. The cache control unit 22includes a determination unit 22A. The determination unit 22A determineswhether or not to cache received contents, based on a predeterminedalgorithm. The “predetermined algorithm” used herein refers to analgorithm for estimating popular contents from the number of times ofcontents request to determine whether or not a cache is required.Therefore, the cache control unit 22 may decide whether to cache thecontents corresponding to a contents name in the Interest packet, basedon the contents name. When it is determined by the determination unit22A that a cache is required, the cache control unit 22 saves thereceived contents in a cache 31. The contents transfer unit 23 transfersthe received contents. The path setting unit 24 sets a short cut pathbased on a pending information table (PIT) and a conversion table to bedescribed later.

The transport layer function 13B includes a transmission controlprotocol (TCP) control unit 25 and a user datagram protocol (UDP)control unit 26. When the quality of service (QoS) of a section path setby the path setting unit 24 has no bandwidth guarantee, the TCP controlunit 25 establishes, as the protocol of the transport layer, forexample, a TCP connection that executes congestion control,retransmission control, etc., on the section path. When the QoS of thesection path set by the path setting unit 24 has any bandwidthguarantee, the UDP control unit establishes, as the protocol of thetransport layer, for example, a UDP connection with small processingload, on the section path without executing congestion control,retransmission control, etc. The IP layer function 13C has an IP controlunit 27 that executes the IP protocol.

Further, an area in the memory for storing various data includes a cache31, a forwarding information base (FIB) 32, a PIT 33, and a conversiontable 34. The cache 31 is an area for caching received contents. The FIB32 is a table for storing Face when transferring the Interest packetcorresponding to the content name to the next hop. The “Face” usedherein is equivalent to IF in the CCN technology. FIG. 3 is anexplanatory view illustrating an example of the entry configuration ofthe FIB 32. FIG. 3 illustrates a #3 FIB 32 in a #3 relay node 4. The #3FIB 32 illustrated in FIG. 3 is an area for storing a contents name 32Aand a transfer destination Face 32B in association with each other. Thecontents name 32A is an identifier for identifying contents. Thetransfer destination Face 32B is Face of a transfer destination to whichthe received Interest packet is transferred.

The PIT 33 is a table used when the received contents are transferred.FIG. 4 is an explanatory view illustrating an example of the entryconfiguration of a #3 PIT 33. FIG. 4 illustrates the #3 PIT 33 in the #3relay node 4. The #3 PIT 33 illustrated in FIG. 4 is an area for storinga contents name 33A and a request source Face 33B in association witheach other. The contents name 33A is an identifier for identifyingcontents. The request source Face 33B is a request source Face of theInterest packet, that is, a transfer destination Face when the receivedcontents are transferred.

The conversion table 34 is a Face-IP conversion table used when therequest source Face and the IP address are converted. FIG. 5 is anexplanatory view illustrating an example of the entry configuration ofthe conversion table 34. FIG. 5 illustrates the conversion table 34 inthe #3 relay node 4. The #3 conversion table 34 illustrated in FIG. 5 isan area for storing a Face 34A and an IP address 34B in association witheach other. The Face 34A is a transfer destination Face when thereceived contents are transferred. The IP address 34B is an IP addresscorresponding to the transfer destination Face.

Each of the relay nodes 4 divides the received contents into, forexample, a predetermined number of divided data, sequentially stores thedivided data in a payload within an IP packet, and sequentiallytransfers a predetermined number of IP packets to the relay node 4 ofthe next hop. The transport layer function 13B in the relay node 4 usesthe IP layer function 13C to sequentially receive a predetermined numberof IP packets from the relay node 4 and acknowledges delivery of thepredetermined number of IP packets. Then, after the acknowledgment ofdelivery of the IP packets, the CCN layer function 13A in the relay node4 aggregates the divided data in the predetermined number of IP packets,as received contents, and stores the received contents in the cache 31.On the other hand, even when the IP router 5 of the IP layer is used ona path on which the received contents are transferred, it is possible tosuppress the transfer rate of the received contents from beingdecreased. The reason for that is because the IP router 5 transfers theIP packets without aggregation or division.

The Interest control unit 21 includes a receiving unit 21A, atransmitting unit 216, and a control unit 21C. The receiving unit 21Areceives an Interest packet from the previous hop. When it is determinedthat a cache is not required, that is the received contents are notsaved in the cache, the transmitting unit 21B determines whether or nota shortcut IP in the Interest packet is added. When it is determinedthat the shortcut IP is not added, the transmitting unit 21B adds an IPaddress of the previous hop to an additional area of the shortcut IP andtransmits the Interest packet with the IP address added thereto to thenext hop. When it is determined that the shortcut IP is added, thetransmitting unit 21B transmits the Interest packet as it is to the nexthop without changing the shortcut IP. When it is determined that a cacheis required, that is the received contents are saved in the cache, thetransmitting unit 21B deletes the shortcut IP in the Interest packet,adds the IP address of its own device to a source address in theInterest packet, and transmits the Interest packet with the IP addressas the source address to the next hop.

The control unit 21C activates an aging timer at a timing referring tothe PIT 33 and the request source Face in the conversion table 34. Whenthe aging timer is timed-up (i.e., expires), the control unit 21Cdeletes the entry of the request source Face from the PIT 33. Further,when the aging timer is timed-up, the control unit 21C deletes the entryof the IP address corresponding to the request source Face from theconversion table 34. As a result, since the entries which are not usedfor a long time in the PIT 33 and the conversion table 34 are deleted,the memory capacity in the PIT 33 and the conversion table 34 may besaved. When the request source Face is referred to again during thecounting of the aging timer, the control unit 21C resets the countingaging timer.

Next, the operation of the CCN system 1 according to the firstembodiment will be described. FIG. 6 is an explanatory view illustratingan example of a processing operation in the CCN system 1 related tocontents request processing. A user terminal 2_#0 transmits an Interestpacket including a contents name “Kawasaki” to a relay node 4_#1. Uponreceiving the Interest packet from the user terminal 2_#0, since therelay node 4_#1 determines that a cache is required, the relay node 4_#1sets the request source Face 33B corresponding to the contents name 33Ain the Interest packet as “Face_#0” to update a PIT 33_#1. Here, Face_#0is a Face addressed to the user terminal 2_#0. Then, the relay node 4_#1refers to “Face_#2” of a transfer destination Face 32B corresponding toa contents name 32A of the Interest packet in a FIB 32_#1 to transferthe Interest packet to a relay node 4_#2. The source address in theInterest packet includes “Face_#1” of the relay node 4_#1.

Upon receiving the Interest packet from the relay node 4_#1, since therelay node 4_#2 determines that no cache is required, the relay node4_#2 adds an IP address corresponding to “Face_#1” of the relay node4_#1 to the shortcut IP in the Interest packet without updating a PIT33_#2. Then, the relay node 4_#2 refers to “Face_#3” as the transferdestination Face 32B corresponding to the contents name 32A of theInterest packet in the FIB 32_#2 to transfer the Interest packet to therelay node 4_#3. The shortcut IP in the Interest packet contains the IPaddress corresponding to “Face_#1” of the relay node 4_#1.

Upon receiving the Interest packet from the relay node 4_#2, since therelay node 4_#3 determines that a cache is required, the relay node 4_#3acquires an IP address corresponding to “Face_#1” from the shortcut IPin the Interest packet. The relay node 4_#3 sets the request source Face33B corresponding to the contents name 33A in the Interest packet as“Temp Face_#1” and updates the PIT 33_#3. Further, the relay node 4_#3deletes the shortcut IP from the Interest packet. Then, the relay node4_#3 refers to “Face_#4” as the transfer destination Face 326corresponding to the contents name 32A of the Interest packet in the FIB32_#3 to transfer the Interest packet to a relay node 4_#4. The sourceaddress in the Interest packet contains “Face_#3” of the relay node4_#3.

Upon receiving the Interest packet from the relay node 4_#3, since therelay node 4_#4 determines that no cache is required, the relay node4_#4 does not update a PIT 33_#4 and determines whether or not there isa shortcut IP in the Interest packet. Since there is no shortcut IP inthe Interest packet, the relay node 4_#4 adds an IP addresscorresponding to “Face_#3,” which is the address of the relay node 4_#3,to the shortcut IP in the Interest packet. Then, the relay node 4_#4refers to “Face_#5” as the transfer destination Face 32B correspondingto the contents name 32A of the Interest packet in the FIB 32_#4 totransfer the Interest packet to a relay node 4_#5. The shortcut IP inthe Interest packet contains the IP address corresponding to “Face_#3”of the relay node 4_#3.

Upon receiving the Interest packet from the relay node 4_#4, since therelay node 4_#5 determines that no cache is required, the relay node4_#5 does not update a PIT 33_#5 and determines whether or not there isa shortcut IP in the Interest packet. Since there is a shortcut IP inthe Interest packet, the relay node 4_#5 maintains the IP addresscorresponding to “Face_#3” of the shortcut IP in the Interest packet.Then, the relay node 4_#5 refers to “Face_#6” as the transferdestination Face 32B corresponding to the contents name 32A of theInterest packet in the FIB 32_#5 to transfer the Interest packet to arelay node 4_#6. The shortcut IP in the Interest packet contains the IPaddress corresponding to “Face_#3” of the relay node 4_#3.

Upon receiving the Interest packet from the relay node 4_#5, since therelay node 4_#6 determines that a cache is required, the relay node 4_#6determines whether or not there is a shortcut IP in the Interest packet.Since there is a shortcut IP in the Interest packet, the relay node 4_#6acquires an IP address corresponding to “Face_#3” of the shortcut IP.Further, the relay node 4_#6 sets the request source Face 33Bcorresponding to the contents name 33A in the Interest packet as “TempFace_#3” and updates the PIT 33_#6. Further, the relay node 4_#6 deletesthe shortcut IP from the Interest packet. Then, the relay node 4_#6refers to “Face_#7” as the transfer destination Face 32B correspondingto the contents name 32A of the Interest packet in the FIB 32_#6 totransfer the Interest packet to the server 3. Here, Face_#7 is a Faceaddressed to the server 3. The source address in the Interest packetcontains “Face_#6” of the relay node 4_#6. As a result, the server 3 mayreceive Interest packets from the user terminal 2_#0.

FIG. 7 is an explanatory view illustrating an example of a processingoperation in the CCN system 1 related to contents transfer processing.Upon receiving the Interest packet from the relay node 4_#6, the server3 illustrated in FIG. 7 transfers request contents of the Interestpacket to the relay node 4_#6.

Upon receiving the request contents of the Interest packet from theserver 3, since the relay node 4_#6 determines that a cache is required,the relay node 4_#6 saves the received contents in the cache 31.Further, the relay node 4_#6 refers to the PIT 33_#6 to acquire “TempFace_#3” as the request source Face 33B corresponding to the contentsname 33A of the received contents. Further, the relay node 4_#6 refersto a conversion table 34_#6 to convert “Temp Face_#3” of the acquiredFace 34A into an IP address 34B “192.168.3.1”.

Further, the relay node 4_#6 forms a shortcut path for the relay node4_#3 based on the IP address 346 corresponding to the Face 34A. In thiscase, the shortcut path is a path of relay node 4_#6→IP router5_#c→relay node 4_#3. The relay node 4_#6 transfers the IP packet of thereceived contents to the IP router 5_#c at the IP layer. Further, the IProuter 5_#c transfers the IP packet of the received contents to therelay node 4_#3.

Upon receiving the received contents from the IP router 5_#c, since therelay node 4_#3 determines that a cache is required, the relay node 4_#3caches the received contents in the cache 31. Further, the relay node4_#3 refers to the PIT 33_#3 to acquire “Temp Face_#1” as the requestsource Face 33B corresponding to the contents name 33A of the receivedcontents. Further, the relay node 4_#3 refers to the conversion table34_#3 to convert “Temp Face_#1” of the Face 34A into an IP address 34B“192.168.1.1.” Further, the relay node 4_#3 forms a shortcut path forthe relay node 4_#1 based on the IP address corresponding to “TempFace_#1” corresponding to the request source Face 33B. In this case, theshortcut path is a path of relay node 4_#3→IP layer function 13C inrelay node_#2→relay node 4_#1. The relay node 4_#3 transfers thereceived contents to the IP layer function 13C in the relay node 4_#2 atthe IP layer.

The IP layer function 13C in the relay node 4_#2 relays the receivedcontents to the relay node 4_#1 at the IP layer. Upon receiving thereceived contents, the relay node 4_#1 refers to the PIT 33_#1 and alsorefers to “Face_#0” as the request source Face 33B corresponding to thecontents name 33A of the received contents to transfer the receivedcontents to the user terminal 2_#0. As a result, the user terminal 2_#0may acquire desired received contents specified by the Interest packet.

The relay node 4_#6 deletes the relay nodes 4_#4 and #5 requiring nocache on a path through which Interest packets are transferred, from theHop-by-Hop communication and forms a shortcut path to the relay node4_#3. The relay node 4_#6 uses this shortcut path to transfer thereceived contents to the IP layer. In other words, as a result ofeliminating the need to pass through the relay nodes 4_#4 and #5, a pathbetween the relay node 4_#6 and the relay node 4_#3 goes through the IProuter 5_#c without going through the relay nodes 4_#4 and #5 and the IProuters 5_#a and #b. If this shortcut path is not used, the IP routers5_#a transfers the IP packets between the relay nodes 4_#3 and the relaynodes 4_#4. If it is not also used, the IP routers 5_#b transfers the IPpackets between the relay nodes 4_#5 and the relay nodes 4_#6. The IProuter 5_#c does not terminate the communication and gets away with onlyIP relaying of the IP packet. In addition, when the QoS allowing theperformance of a path of relay node 4_#6→IP router 5_#c→relay node 4_#3is set to no bandwidth guarantee, a TCP is selected as a transportprotocol. Then, the TCP control unit 25 in the relay node 4_#6establishes a TCP connection in the shortcut path to the relay node 4_#3and uses the TCP connection to transfer the received contents.

The relay node 4_#3 deletes the relay node 4_#2 requiring no cache on apath through which Interest packets are transferred, from the Hop-by-Hopcommunication and forms a shortcut path to the relay node 4_#1. Therelay node 4_#3 uses this shortcut path to transfer the receivedcontents to the IP layer. In other words, as a result of eliminating theneed to pass through the CCN layer function 13A of the relay node 4_#2,a path between the relay node 4_#3 and the relay node 4_#1 goes throughthe IP layer function 13C of the relay node 4_#2 without going throughthe CCN layer function 13A of the relay node 4_#2. Moreover, when usingthe CCN layer function 13A in the relay node 4_#2, it is necessary toterminate the communication once and replace it with a newcommunication. That is, the CCN layer function 13A utilizes the IP layerfunction 13C to collect IP packets storing the divided data of thereceived contents, forms the received contents with the divided data inthe collected IP packets, and saves the received contents in the cache31. In contrast, the IP layer function 13C does not terminate thecommunication and gets away with only IP relaying of the IP packetstoring the divided data of the received contents to the next hop withthe same granularity. When the QoS allowing the performance of a path ofrelay node 4_#3→IP layer function 13C of relay node 4_#2→relay node 4_#1is set to be a bandwidth guarantee, a UDP is selected as a transportprotocol. Then, the UDP control unit 26 in the relay node 4_#3establishes a UDP connection in the shortcut path to the relay node 4_#1and uses the UDP connection to transfer the received contents.

FIG. 8 is a sequence diagram illustrating an example of a processingoperation of the CCN system 1 from contents request to contentsacquisition. The user terminal 2_#0 illustrated in FIG. 8 notifies anInterest packet to the relay node 4_#1 (operation S11). The Interestcontrol unit 21 in the relay node 4_#1 receives the Interest packet fromthe user terminal 2. Then, the cache control unit 22 in the relay node4_#1 determines whether or not a cache is required, based on a contentsname in the Interest packet. When it is determined that a cache isrequired (operation S12), the Interest control unit 21 in the relay node4_#1 transfers the Interest packet to the relay node 4_#2 (operationS13).

The cache control unit 22 in the relay node 4_#2 receives the Interestpacket from the relay node 4_#1 and determines whether or not a cache isrequired, based on a contents name in the Interest packet. When it isdetermined that no cache is required (operation S14), the Interestcontrol unit 21 in the relay node 4_#2 adds an IP address correspondingto “Face_#1” of the relay node 4_#1, which is the previous hop, to ashortcut IP in the Interest packet (operation S15). The Interest controlunit 21 in the relay node 4_#2 transfers the Interest packet with the IPaddress corresponding to “Face_#1” added to the shortcut IP to the relaynode 4_#3 (operation S16).

The cache control unit 22 in the relay node 4_#3 receives the Interestpacket from the relay node 4_#2 and determines whether or not a cache isrequired, based on a contents name in the Interest packet. When it isdetermined that a cache is required (operation S17), the Interestcontrol unit 21 in the relay node 4_#3 updates an IP addresscorresponding to “Face_#1” of the shortcut IP to the PIT 33_#3 and theconversion table 34_#3 (operation S18). The PIT 33_#3 updates thecontents name “Kawasaki” and the request source Face “Temp Face_#1.” Theconversion table 34_#3 updates the IP address of the shortcut IP and“Temp Face_#1.” The Interest control unit 21 in the relay node 4_#3deletes the shortcut IP from the Interest packet (operation S19) andtransfers the Interest packet to the relay node 4_#4 (operation S20).

The cache control unit 22 in the relay node 4_#4 receives the Interestpacket from the relay node 4_#3 and determines whether or not a cache isrequired, based on a contents name in the Interest packet. When it isdetermined that no cache is required (operation S21), the Interestcontrol unit 21 in the relay node 4_#4 adds an IP address correspondingto “Face_#3” of the relay node 4_#3, which is the previous hop, to theshortcut IP in the Interest packet (Operation S22). The Interest controlunit 21 in the relay node 4_#4 transfers the Interest packet with the IPaddress corresponding to “Face_#3” added to the shortcut IP to the relaynode 4_#5 (operation S23).

The cache control unit 22 in the relay node 4_#5 receives the Interestpacket from the relay node 4_#4 and determines whether or not a cache isrequired, based on a contents name in the Interest packet. When it isdetermined that no cache is required (operation S24), the Interestcontrol unit 21 in the relay node 4_#5 does not update the shortcut IPin the Interest packet (operation S25) and transfers the Interest packetto the relay node 4_#6 (operation S26). The cache control unit 22 in therelay node 4_#6 receives the Interest packet from the relay node 4_#5and determines whether or not a cache is required, based on a contentsname in the Interest packet. When it is determined that a cache isrequired (operation S27), the Interest control unit 21 in the relay node4_#6 updates an IP address corresponding to “Face_#3” of the shortcut IPto the PIT 33_#6 and the conversion table 34_#6 (operation S28). The PIT33_#6 updates the contents name “Kawasaki” and the request source Face“Temp Face_#3.” The conversion table 34_#6 updates the IP address of theshortcut IP and “Temp Face_#3.” The relay node 4_#6 deletes the shortcutIP from the Interest packet (operation S29) and transfers the Interestpacket to the server 3 (operation S30).

Upon receiving the Interest packet, the server 3 acquires contentscorresponding to the contents name in the Interest packet from a storagedestination and transfers the acquired contents to the relay node 4_#6(operation S31). Upon receiving the contents, the path setting unit 24in the relay node 4_#6 sets a shortcut path for the relay node 4_#3based on the PIT 33_#6 and the conversion table 34_#6 (operation S32).As for the shortcut path, a path of relay node 4_#6→IP router 5_#c→relaynode 4_#3 is set, and a TCP is selected since a bandwidth guarantee isabsent in the shortcut path.

The contents transfer unit 23 in the relay node 4_#6 uses the set pathto transfer the received contents to the relay node 4_#3 (operationS33). At this time, upon receiving the received contents from the relaynode 4_#6, the IP router 5_#c on the shortcut path refers to a routingtable of the IP layer to pass the IP packet of the received contents andtransfers the passed IP packet to the relay node 4_#3 (operation S34).

Upon receiving the received contents, the path setting unit 24 in therelay node 4_#3 sets a shortcut path for the relay node 4_#1 based onthe PIT 33_#3 and the conversion table 34_#3 (operation S35). As for theshortcut path, a path of relay node 4_#3→IP layer function 13C in relaynode 4_#2→relay node 4_#1 is set, and a UDP is selected since abandwidth guarantee is present in the shortcut path. The IP layerfunction 13C in the relay node 4_#2 passes the IP packet of the receivedcontents from the relay node 4_#3 and transfers the passed IP packet ofthe received contents to the relay node 4_#1 (operation S36).

Further, the content transfer unit 23 in the relay node 4_#1 receivesthe received contents from the IP layer function 13C in the relay node4_#2 and transfers the received contents to the user terminal 2(operation S37).

FIG. 9 is a flowchart illustrating an example of a processing operationof the relay node 4 related to reception processing. The Interestcontrol unit 21 in the relay node 4 illustrated in FIG. 9 determineswhether or not an Interest packet has been received (operation S41).When it is determined that an Interest packet has been received (“Yes”in operation S41), the Interest control unit 21 in the relay node 4determines whether or not contents are saved in the cache 31 (operationS42).

When it is determined that no contents are saved in the cache 31 (“No”in operation S42), the cache control unit 22 in the relay node 4determines whether or not a cache is required (operation S43). When itis determined the no cache is required (“Not required” in operationS43), the Interest control unit 21 in the relay node 4 determineswhether or not a shortcut IP is added to the Interest packet (operationS44). When it is determined that a shortcut IP is not added to theInterest packet (“No” in operation S44), the Interest control unit 21 inthe relay node 4 adds a shortcut IP of the previous hop to the Interestpacket (operation S45). The Interest control unit 21 transfers theInterest packet to the next hop (operation S46). Then, the Interestcontrol unit 21 in the relay node 4 transfers the Interest packet to thenext hop and then ends the processing operation illustrated in FIG. 9.When it is determined that a shortcut IP is added to the Interest packet(“Yes” in operation S44), the Interest control unit 21 in the relay node4 proceeds to the operation S46 so as to transfer the Interest packet tothe next hop without changing the shortcut IP.

When it is determined that a cache is required (“Required” in operationS43), the Interest control unit 21 in the relay node 4 determineswhether or not a shortcut IP is added to the Interest packet (operationS47). When it determined that no shortcut IP is added to the Interestpacket (“No” in operation S47), the relay node 4 updates the PIT 33 witha Face of the previous hop as a request source Face (operation S48).Then, the relay node 4 proceeds to the operation S46 so as to transferthe Interest packet to the next hop.

When it is determined that the shortcut IP is added to the Interestpacket (“Yes” in operation S47), the Interest control unit 21 updatesthe PIT 33 with a Face corresponding to an IP address added to theshortcut IP as a request source Face (operation S49). Further, theInterest control unit 21 in the relay node 4 updates the conversiontable 34 (operation S50), deletes the shortcut IP of the Interest packet(operation S51), and proceeds to the operation S46 so as to transfer theInterest packet to the next hop.

When it is determined that contents are saved in the cache 31 (“Yes” inoperation S42), the Interest control unit 21 in the relay node 4determines whether or not a shortcut IP is added to the Interest packet(operation S52). When it is determined that a shortcut IP is added tothe Interest packet (“Yes” in operation S52), the Interest control unit21 in the relay node 4 updates the conversion table 34 (operation S53).Furthermore, the path setting unit 24 in the relay node 4 sets ashortcut path based on the contents of the conversion table 34(operation S54). The contents transfer unit 23 in the relay node 4distributes the received contents after setting the path (operationS55), and ends the processing operation illustrated in FIG. 9.

When it is determined that no shortcut IP is added to the Interestpacket (“No” in operation S52), the path setting unit 24 in the relaynode 4 proceeds to operation S54 so as to set a shortcut path based onthe contents of the conversion table 34.

FIG. 10 is a flowchart illustrating an example of a processing operationof the relay node 4 related to contents relay processing. The cachecontrol unit 22 in the relay node 4 illustrated in FIG. 10 determineswhether or not contents have been received (operation S61). When it isdetermined that contents have been received (“Yes” in operation S61),the cache control unit 22 in the relay node 4 saves the receivedcontents in the cache 31 (operation S62). Further, when the receivedcontents are saved in the cache 31, the path setting unit 24 in therelay node 4 refers to the contents of the PIT 33 and the conversiontable 34 to set a shortcut path for transferring the received contents(operation S63).

The contents transfer unit 23 in the relay node 4 updates the contentsof the PIT 33 (operation S64), transfers the received contents to therequest source Face (operation S65), and ends the processing operationillustrated in FIG. 10. When it is determined that no contents have beenreceived (“No” in operation S61), the relay node 4 ends the processingoperation illustrated in FIG. 10.

Upon receiving the contents, the relay node 4 saves the receivedcontents in the cache 31. The relay node 4 sets a shortcut path of thereceived contents based on a request source Face corresponding to thereceived contents in the PIT 33 and the conversion table 34 and an IPaddress corresponding to the request source Face. Further, the relaynode 4 transfers the received contents via the shortcut path.

In the CCN system 1 according to the first embodiment, among relay nodes4 on a path through which Interest packets are transferred, a relay node4 requiring no cache is deleted to form a shortcut path. As a result, itis possible to execute optimal routing from the server 3 or a relay node4 that stores the received contents in the cache 31 to the user terminal2, thereby increasing the transfer rate of the received contents.

In the CCN system 1, since the received contents are transferred to theIP layer even under the condition that relay nodes 4 and IP routers 5are mixed in a shortcut path, the transfer rate of the received contentsmay be increased.

Further, in the CCN system 1, when QoS of the shortcut path fortransferring the received contents has no bandwidth guarantee, a TCPconnection is established on the shortcut path. As a result, thecongestion control and retransmission control may be ensured on theshortcut path for transferring the received contents.

Further, in the CCN system 1, when the QoS of the shortcut path fortransferring the received contents has bandwidth guarantee, a UDPconnection is established on the shortcut path. As a result, it isunnecessary to execute congestion control and retransmission control onthe shortcut path for transferring the received contents, therebysuppressing the processing load.

Second Embodiment

FIG. 11 is an explanatory view illustrating an example of a processingoperation from contents request to contents acquisition of a CCN system1A according to a second embodiment. In FIG. 11, the same components asthose of the CCN system 1 of the first embodiment will be denoted by thesame reference numerals as used in the first embodiment, and explanationthereof will be omitted.

It is assumed that the relay nodes 4_#1 to #6 in the CCN system 1Aillustrated in FIG. 11 have saved contents including the contents name“Kawasaki” in their respective caches 31. In the CCN system 1A, anInterest packet including the contents name “Kawasaki” is transmittedfrom a user terminal 2_#100 to a relay node 4_#10.

Upon receiving the Interest packet from the user terminal 2_#100, sincethe relay node 4_#10 determines that no cache is required, a CCN layerfunction 13A in the relay node 4_#10 does not update a PIT 33_#10.Further, the CCN layer function 13A adds an IP address corresponding to“Face_#100” of the user terminal 2_#100 to a shortcut IP in the Interestpacket. Then, the relay node 4_#10 refers to “Face_#2” as a transferdestination Face 32B corresponding to a contents name 32A of theInterest packet in a FIB 32_#10 to transfer the Interest packet to therelay node 4_#2.

Upon receiving the Interest packet including the IP addresscorresponding to “Face_#100” as the shortcut IP, the relay node 4_#2determines whether or not the contents of the contents name has beensaved in the cache 31, based on the contents name in the Interestpacket. When it is determined that the contents have been saved in thecache 31, the relay node 4_#2 determines whether or not a shortcut IP isadded to the Interest packet. When it is determined that a shortcut IPis added, the relay node 4_#2 updates the IP address corresponding to“Face_#100” of the shortcut IP to the PIT 33 and the conversion table34. The PIT 33_#2 updates the contents name “Kawasaki” and “Face_#100.”The conversion table 34_#2 updates the shortcut IP and “Face_#100.” Therelay node 4_#2 acquires from the cache 31 the received contentscorresponding to the contents name in the Interest packet. Further, therelay node 4_#2 forms a shortcut path to the user terminal 2_#100 basedon an IP address corresponding to a request source Face (Face_#100)corresponding to the contents name in the PIT 33. In this case, theshortcut path is a path of relay node 4_#2→IP layer function 13C ofrelay node 4_#10→user terminal 2_#100. When QoS on the shortcut path ofrelay node 4_#2→IP layer function 13C of relay node 4_#10→user terminal2_#100 has no bandwidth guarantee, the relay node 4_#2 establishes a TCPconnection in the shortcut path. The relay node 4_#2 transfers the IPpacket of the received contents to the IP layer function 13C of therelay node 4_#10 at the IP layer.

The IP layer function 13C of the relay node 4_#10 transfers the receivedcontents from the relay node 4_#2 to the user terminal 2_#100 at the IPlayer. As a result, since the IP layer function 13C of the relay node4_#10 does not pass through the CCN layer function 13A, the IP layerfunction 13C gets away with only IP relaying of the IP packet of thereceived contents to the IP layer. Then, the user terminal 2_#100 mayacquire the received contents from the relay node 4_#2 via the IP layerfunction 13C of the relay node 4_#10.

In the CCN system 1A according to the second embodiment, under thecondition that a relay node 4 on a path from the user terminal 2_#100 tothe server 3 caches contents, the CCN layer function 13A of the relaynode 4_#10 requiring no cache is excluded from Hop-by-Hop communication.Then, the CCN system 1A may increase the transfer rate of the contentswhile selecting a suitable transport protocol according to the setcontents of the QoS allowing the performance of the shortcut path.

Third Embodiment

FIG. 12 is an explanatory view illustrating an example of a processingoperation from contents request to contents acquisition of a CCN system1B according to a third embodiment. In FIG. 12, the same components asthose of the CCN system 1 of the first embodiment will be denoted by thesame reference numerals as used in the first embodiment, and explanationthereof will be omitted.

The CCN system 1B illustrated in FIG. 12 replaces the server 3 storingcontents with a temperature sensor node 3A that detects a temperature ascontents and stores temperature data as a result of the detection. Thetemperature sensor node 3A is a node capable of communicating with therelay nodes 4 and the IP routers 5.

It is assumed that the user terminal 2#0 desires data such as the latesttemperature detected by the temperature sensor node 3A, rather than thecontents stored in the caches 31 in the relay nodes 4.

The user terminal 2_#0 adds an express flag to an Interest packetincluding a contents name “/sensor/temperature” and transmits theInterest packet to the relay node 4_#1. Upon receiving the Interestpacket, the relay node 4_#1 determines that no contents cache isrequired, based on the express flag in the Interest packet. Further, therelay node 4_#1 adds an IP address corresponding to Face_#0 of the userterminal 2_#0 to the shortcut IP in the Interest packet and transfersthe Interest packet to the relay node 4_#2 of the next hop.

Upon receiving the Interest packet from the relay node 4_#1, the relaynode 4_#2 determines that no contents cache is required, based on theexpress flag in the Interest packet. Further, the relay node 4_#2determines whether or not a shortcut IP in the Interest packet is added.When it is determined that a shortcut IP is added, the relay node 4_#2transfers the Interest packet to the relay node 4_#3, which is the nexthop, without changing the shortcut IP (IP address corresponding toFace_#0).

Upon receiving the Interest packet from the relay node 4_#2, the relaynode 4_#3 determines that no contents cache is required, based on theexpress flag in the Interest packet. Further, the relay node 4_#3determines whether or not a shortcut IP in the Interest packet is added.When it is determined that a shortcut IP is added, the relay node 4_#3transfers the Interest packet to the relay node 4_#4, which is the nexthop, without changing the shortcut IP (IP address corresponding toFace_#0).

Upon receiving the Interest packet from the relay node 4_#3, the relaynode 4_#4 determines that no contents cache is required, based on theexpress flag in the Interest packet. Further, the relay node 4_#4determines whether or not a shortcut IP in the Interest packet is added.When it is determined that a shortcut IP is added, the relay node 4_#4transfers the Interest packet to the relay node 4_#5, which is the nexthop, without changing the shortcut IP (IP address corresponding toFace_#0).

Upon receiving the Interest packet from the relay node 4_#4, the relaynode 4_#5 determines that no contents cache is required, based on theexpress flag in the Interest packet. Further, the relay node 4_#5determines whether or not a shortcut IP in the Interest packet is added.When it is determined that a shortcut IP is added, the relay node 4_#5transfers the Interest packet to the relay node 4_#6, which is the nexthop, without changing the shortcut IP (IP address corresponding toFace_#0).

Upon receiving the Interest packet from the relay node 4_#5, the relaynode 4_#6 determines that no contents cache is required, based on theexpress flag in the Interest packet. Further, the relay node 4_#6determines whether or not a shortcut IP in the Interest packet is added.When it is determined that a shortcut IP is added, the relay node 4_#6transfers the Interest packet to the temperature sensor node 3A, whichis the next hop, without changing the shortcut IP (IP addresscorresponding to Face_#0).

Upon receiving the Interest packet, the temperature sensor node 3Adetermines whether or not temperature data corresponding to a contentsname has been saved in the cache, based on the contents name in theInterest packet. When it is determined that temperature datacorresponding to a content name has been stored in the cache, thetemperature sensor node 3A forms a shortcut path based on a shortcut IPin the Interest packet, that is, an IP address of the user terminal2_#0. In this case, the shortcut path is a path of temperature sensornode 3A→IP router 5_#d→user terminal 2_#0. Further, the QoS allowing theperformance of the shortcut path is assumed to have a bandwidthguarantee.

The temperature sensor node 3A establishes a UDP connection on theshortcut path and transfers the temperature data to the IP router 5_#dwith the UDP connection. Further, the IP router 5_#d uses the UDPconnection to transfer the received temperature data to the userterminal 2_#0.

In the CCN system 1B according to the third embodiment, by adding theexpress flag to the Interest packet, the relay nodes 4 on a path throughwhich Interest packets are transferred is instructed not to require acache. In the CCN system 1B, the relay nodes 4_#1 to #6 on a pathbetween the user terminal 2_#0 and the temperature sensor node 3A aredeleted to form a shortcut path. The temperature sensor node 3Atransfers the temperature data to the user terminal 2_#0 via the IProuter 5_#d on the shortcut path. As a result, the user terminal 2_#0may increase the transfer rate when transferring the latest temperaturedata from the temperature sensor node 3A.

In addition, each component of the respective illustrated units is notnecessarily required to be configured physically as illustrated in thedrawings. That is, specific forms of distribution and integration of theindividual units are not limited to those illustrated in the drawings,and all or some of the units may be configured to be distributed orintegrated functionally or physically in arbitrary units according tovarious loads, usage conditions, etc.

Furthermore, all or some of the various processing functions performedin each device may be executed on a CPU (or a microcomputer such as amicro processing unit (MPU) or a micro controller unit (MCU)). Inaddition, it is to be understood that all or some of the variousprocessing functions may be executed on a program that is analyzed andexecuted by a CPU (or a microcomputer such as an MPU or an MCU), or onhardware by wired logic.

All examples and conditional language recited herein are intended forpedagogical purposes to aid the reader in understanding the inventionand the concepts contributed by the inventor to furthering the art, andare to be construed as being without limitation to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification relate to an illustrating of thesuperiority and inferiority of the invention. Although the embodimentsof the present invention have been described in detail, it should beunderstood that the various changes, substitutions, and alterationscould be made hereto without departing from the spirit and scope of theinvention.

What is claimed is:
 1. A relay apparatus comprising: a memory; and aprocessor coupled to the memory and the processor configured to: receivea first packet including an identifier for indicating a content;determine whether or not the content indicated by the identifierincluded in the first packet is saved in a cache; transmit a secondpacket including a source address of the first packet and the identifierwhen it is determined that the content is not saved in the cache; andtransmit a third packet including an address of the relay apparatus andthe identifier when it is determined that the content is saved in thecache.
 2. The relay apparatus according to claim 1, wherein theprocessor is configured to: store the source address of the first packetas an address of a request source corresponding to the identifier; andset a path on which the content corresponding to the identifier istransferred, based on the stored source address corresponding to theaddress of the request source.
 3. The relay apparatus according to claim2, wherein the processor is configured to: set a transmission controlprotocol (TCP) when the set path has quality of service (QoS) with nobandwidth guarantee; and set an user datagram protocol (UDP) when theset path has the QoS with a bandwidth guarantee.
 4. The relay apparatusaccording to claim 1, wherein the processor is configured to determinewhether or not the content indicated by the identifier is saved in thecache, based on a presence or absence of a predetermined flag in thefirst packet.
 5. The relay apparatus according to claim 2, wherein theprocessor is configured to delete the stored source addresscorresponding to the address of the request source with a lapse of apredetermined time after referring to the stored source address.
 6. Arelay method comprising: receiving a first packet including anidentifier for indicating a content; determining whether or not thecontent indicated by the identifier included in the first packet issaved in a cache; transmitting a second packet including a sourceaddress of the first packet and the identifier when it is determinedthat the content is not saved in the cache; and transmitting a thirdpacket including an address of the relay apparatus and the identifierwhen it is determined that the content is saved in the cache, by aprocessor.